Direct & Inverse Proportion
When more means more, when more means less, and how to tell them apart.
What this lesson covers
Direct & Inverse Proportion is a 10-part Class 8 Mathematics lesson. Each part makes one point and then hands over to the next, so it can be read in a sitting or picked up again at the part you stopped on. It defines the idea in plain words before using it, works through an example step by step, breaks the topic into its parts and compares them, shows where it is used outside the textbook, names the mistakes that cost marks in an exam, ends with a recap of what to remember.
How it begins
Direct proportion: as one quantity increases, the other increases in the same ratio. Double one, double the other. y ∝ x → y = kx y ÷ x is always the sameInverse proportion: as one increases, the other decreases proportionally. Double one, halve the other. y ∝ 1/x → y = k/x y × x is always the sameThe k is the constant of proportionality.
The 10 parts
- Two kinds of relationship
- How to tell which you have
- The graphs look completely different
- A direct proportion problem
- An inverse proportion problem
- Proportion to a power
- Proportion in daily life
- Where it usually goes wrong
- What to remember
- Watch one worked through
Practise Direct & Inverse Proportion
Everything on QuizByt for Class 8 Mathematics that goes with this lesson: read it first, then test yourself while it is fresh.
🧠 5 quizzes on Direct & Inverse Proportion (2 easy, 2 medium, 1 hard)
Work up from easy to hard: the hard quiz asks the Class 8 exam-style questions on Direct & Inverse Proportion.
🖨️ Printable worksheet
Direct & Inverse Proportion on paper for Class 8, with room to write the working out. Preview the first page free.
🎮 Games for Class 8 Mathematics
Number and logic games at the right level for Class 8. Passing a quiz on Direct & Inverse Proportion earns the credits that open them.
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